"I read somewhere that it is worms that create the topsoil on the ground."

Not quite. The worms help to create topsoil, but so do all kinds of other insects, arthropods, fungi, bacteria, & etc., often collectively known as "the microherd", all working together to break down organic material and turn it into finished compost. Topsoil is this composted organic material (which includes, but is not only, worm castings) mixed with mineral soil, preferably with a few million or billion head of the microherd along for the ride :)

The best way to get topsoil of to add compost to, or compost right on top of, your existing soil. Buying topsoil is second-best, because 1) it costs money, b) the commercial topsoils have been sterilized and thus have no beneficial microherd, and iii) there are no real standards for "topsoil" so the quality can vary widely.

The best way to get worm castings is to raise worms. Buying worm castings is second-best, because 1) it costs money, b) the commercial worm castings have been sterilized and thus have no live beneficial organisms (which unsterilized worm castings are chock full of) , and iii) IMHO, raising your own worms is too much fun to leave to others :)

- Evelyn

I just went out for a little walk in the rain and added a few wormies to my bin.

what you read is 'folk lore' - topsoil is a product of geologic and atmospheric activity over the millenia - worms in N America are newcomers, but they do help 'till' and aereate the existing soil, and are indicators of the microbial activity & health of the soil - purchased topsoil is simply soil [usually 'dirt'] that's been skimmed off somewhere and bagged up, and as it's usually fairly low fertility stuff, and frequently has sand added to 'bulk it up', there were most likely no worms involved anyway!

Bill

Bill